The same unimaginative quality made the Romans leave the seaways of the Mediterranean undeveloped. When presently the barbarians pressed down to the warm water, we read of no swift transport of armies from Spain or Africa or Asia to the rescue of Italy and the Adriatic coasts. Instead, we see the Vandals becoming masters of the western Mediterranean without so much as a naval battle.
The Romans had been held at the Euphrates by an array of mounted archers. It was clear that as the legion was organized it was useless in wide open country, and it should have been equally clear that sooner or later the mounted nomads of east Germany, south Russia, or Parthia were bound to try conclusions with the empire. But the Romans, two hundred years after Cæsar's time, were still marching about, the same drilled and clanking cohorts they had always been, easily ridden round and shot to pieces. The empire had learnt nothing even from Carrhæ.
The incapacity of the Roman imperialism for novelty in methods of transport again is amazing. It was patent that their power and unity depended upon the swift movement of troops and supplies from one part of the empire to another. The republic made magnificent roads; the empire never improved upon them. Four hundred years before the Antonines, Hero of Alexandria had made the first steam-engine. Beautiful records of such beginnings of science were among the neglected treasures of the rich men's libraries throughout the imperial domains. They were seed lying on stony ground. The armies and couriers of Marcus Aurelius drudged along the roads exactly as the armies of Scipio Africanus had done three centuries before them.
The Roman writers were always lamenting the effeminacy of the age. It was their favourite cant. They recognized that the free men of the forest and steppes and desert were harder and more desperate fighters than their citizens, but the natural corollary of developing the industrial power of their accumulations of population to make a countervailing equipment never entered their heads. Instead they took the barbarians into their legions, taught them the arts of war, marched them about the empire, and returned them, with their lesson well learnt, to their own people.